1. Field of the Invention:
This invention relates to the field of seed planters and is particularly directed toward seed planters of the type incorporating a suction pump in conjunction with the seed pickup mechanism.
2. Description of the Prior Art:
The type planter which accounts for most of those in use today is known as the plate type which operates as follows. The frame of the planter is attached by suitable means to a tractor or the like and riding on a press wheel is thus drawn over the ground. A plowshare opens a furrow into which seeds coming through a drop tube fall. The rim of the press wheel being of cross section suitable for accomplishing same causes the furrow to be closed over the seeds and thus the planting process is completed.
It becomes immediately obvious that some means must be provided to select and drop individual seeds at regular intervals in order that not only will the plants be at the desired spacing but that there will be but one plant per space inasmuch as two or more seeds at the same location will result in inferior growth and development. The plate type planter accomplishes this task by means of a rotating plate which has a series of holes disposed about its rim. Seeds contained in the hopper will find their way into these pockets as the plate rotates. As the pockets pass under a shelflike ledge, they are isolated from the rest of the hopper allowing the seeds to fall through the drop tube and into the ground. Power to drive the plate is obtained by coupling the plate through its drive shaft to a set of bevel gears which in turn are driven by means of a chain and sprocket drive which will transmit torque generated by the press wheel as the unit is pulled across the ground.
The disadvantages of the above system are many but resolve themselves into two general categories which are: (1) poor performance in selecting individual seeds and (2) damage to seeds thus preventing germination. More specifically, the ability of this system to select an individual seed is dependent entirely on a good match between seed size and pocket size. This requires that the operator have available to him a selection of plates so as to be able to match size and shape of seed to plate. It follows that regardless of plate availability, satisfactory results will not be obtained unless the seeds are of reasonably uniform size and shape. Such seed is available but at cost premiums varying directly with size consistency.
If a seed is oversize or if it happens to seat in the pocket improperly or if two seeds are lodged in the same pocket, the possibility exists of crushing these seeds as the plate moves under the shelflike ledge, which is the second major disadvantage of this system. Germination of some seeds, peanuts in particular, will not take place if the seeds are even slightly bruised.
Vacuum wheel type seed planters overcome the disadvantages of the plate type in that once the seed has been picked up by the wheel it does not have to come in contact with any other part of the machine until it is dropped and will thus be much less subject to damage. Furthermore, one size of vacuum port will idealistically handle quite a wide range of seed sizes and shapes and hopefully grading should become unnecessary resulting in a savings in seed cost. The principle of vacuum seed selection and handling is not new, there having been several units placed on the market in recent years. They have not, however, been large successes because of several problems which seem to manifest themselves in a failure of each port to pick up and discharge a seed on each revolution of the vacuum wheel with necessary or acceptable consistency. The following are some of the problems which result in erratic or inconsistent performance of the prior vacuum wheel seed planters.
1. Failure to maintain negative pressure within the vacuum wheel to a degree which will cause seed to adhere to port until reaching the drop point.
2. Improper surface configuration in and around port opening. In other words, for maximum holding power, the ideal situation would be for the seed to completely block the port to which it is being held. To the extent that this is not done, holding power is commensurately reduced. The seeds at best are irregular spheroids and at worst may even have convoluted surfaces making good contact between seed and port difficult.
3. Blockage of the nozzles or ports by foreign matter. Obviously, seed stock is going to contain a percentage of foreign matter, consisting of leaves, stalks, husks, broken seed, etc. These materials can be sufficiently small to where they can become lodged in the nozzle or port which renders it inoperative thus causing a skip in the planting pattern.
4. Failure of seed to drop off the wheel at the desired drop point. This problem also causes a skip in the planting pattern.
5. Seeds being stripped off by other seeds as the wheel withdraws from the bed of seeds. In most vacuum wheel systems, the wheel dips into or runs partially submerged in a bed of seeds. That the nozzles come into intimate contact with the seeds there can be no doubt and pick up should be positive. Unfortunately, as a particular seed is withdrawn it can be seen that the possibility exists that it can be stripped off by wiping action or interference from other seeds and there can be no assurance that another seed will be picked up before that particular nozzle is too far from the bed to accomplish same.
Various approaches or solutions to problems have heretofore been made for certain of the above-mentioned problems, a few of which are: first, the U.S. Patent to Clow, No. 3,240,175 incorporates ramlike structure directed towards solving blockage of the nozzles by foreign matter. Clow approaches this problem by incorporating hollow needles as pickup orifices and provides means for cleaning the inside of each needle during the operation.
A second solution concerns failure of the seed to drop off the wheel at the desired point. One solution to this problem was approached by a U.S. Patent to Anderson No. 2,737,314 which incorporates an air jet to blast the seeds from the pickup mechanism. Specifically, the device according to the '314 patent has the suction engaged seeds riding upwardly with rotation of the seed pickup mechanism. They subsequently pass between a nozzle and a funnel where an air jet or blast from the nozzle drives each seed free of the pickup mechanism and directs it into the funnel.
A third solution concerns the seeds being stripped off by other seeds as the wheel withdraws from the bed of seeds. Anderson possibly was aware of this problem since the above-mentioned Anderson '314 patent teaches liquid fluidization of the seeds. Although, this problem was not stated in this patent, the structure incorporated therewith inherently alleviates this problem. More specifically, the '314 patent includes an open topped tank which carries a quantity of water and the seeds, being germinated, remain sunk in the water. The seed pickup mechanism reaches into the bottom of the tank to engage and pick up a seed. Since the seeds are submerged in water and have a certain amount of buoyancy, they do not have the capability of stripping the picked up seed from the pickup mechanism. It should be mentioned that none of the above patents suggest or disclose applicant's device.